Not Even Wrong

It has been almost exactly a year since Hawking gave a talk in Dublin claiming to have found a resolution of the black hole information paradox. Tonight a preprint giving some details of his argument has appeared.

I’ll leave to the quantum gravity experts the evaluation of exactly how convincing Hawking’s argument is. It is based on using the Euclidean quantum gravity framework, which Hawking refers to as “the only sane way to do quantum gravity non-perturbatively”. I’ve always been fond of the idea that you have to think about QFTs using a Euclidean signature for the background, so I wouldn’t argue with him about this point, but I assume others will.

Sean Carroll, of Preposterous Universe, has joined forces with Mark Trodden (of Orange Quark), and new bloggers SLAC particle phenomenologist JoAnne Hewett, USC string/brane theorist Clifford Johnson, and Chicago cosmologist Risa Wechsler. They’ll be collaborating on a new weblog entitled Cosmic Variance, and I’m looking forward to following what they do with it.

This may be part of a new trend of consolidation in the physics weblogging industry, following the lead of the String Coffee Table and the massive, multi-national, government-subsidized Quantum Diaries site. Will small, independent, artisanal producers like myself be able to compete with huge combines like Cosmic Variance, with their professional software and expensive ($6.95/month!) web-hosting services? Or will we be driven out of business as our profit margins are squeezed to the vanishing point? Wait a minute, I’m not making a profit at this anyway…

Actually, today I’m in Austin, Texas on personal business. I suppose I should be looking up Jacques to see if he, Lubos and I can organize an even bigger competing organization.

A colleague informs me that the latest New York Review of Books contains a letter from one of the most well-known mathematicians in the U.S.

Most of the talks at Strings 2005 about the landscape have now taken place, although there’s at least one more this afternoon by Dine. Frederik Denef gave a survey talk entitled Constructions and distributions of string vacua. One amusing thing he does is note that even in toy models with these exponentially large numbers of states, counting the number of states with vacuum energy less than some bound is computationally an NP-hard problem. He describes a wide range of constructions that people have come up with to fix the moduli, concluding that you can “throw enough ingredients together to get sufficiently complicated potential, and this will fix moduli, at least at effective field theory level”, but that these constructions are “ugly”. He then goes on to survey various results about the statistical distributions of these states, and ends by announcing a workshop in Trieste next spring on “String Vacua and the Landscape.”

The talk on Is the number of string theory vacua finite? by Michael Douglas makes Denef’s survey of distributions of vacua kind of pointless. The number of such vacua is definitely infinite, which ruins ones ability to get a probability distribution by counting vacua. Douglas hopes that by putting in a cutoff on the diameter and volume of the compactification space, as well as the size of the vacuum energy, he can make the number of vacua finite. He explains this conjecture, for which the evidence is not very compelling.

Even if he gets the finiteness he hopes for after imposing these cutoffs, the problem then is that the distributions of vacua depend strongly on the cutoff and are peaked at the cutoff value. This is what happens in examples that Kachru talked about at the conference. Douglas is reduced to arguing that “it seems a priori plausible that cosmological selection could depend on the volume of the extra dimensions”, i.e., that somehow the Big Bang would get rid of the problem that his program is predicting large compactification spaces when he wants small ones. There seems to be no reason for this other than wishful thinking. One thing is clear though now: it makes no sense to spend time computing distributions of these vacua, since this gives a result you don’t want. In this game though, it’s not like you give up on your research program when it gives results that don’t look at all like the real world.

The August issue of Discover magazine is out, with a cover story entitled “Is String Theory About to Snap?”. The editors of the magazine describe how they recently became aware of the controversy over string theory when they organized a celebration of Einstein in Aspen last summer. They quote Lawrence Krauss as telling them “String theory may be in a worse position now regarding being testable than it has been at any time in the past 20 years.” To get a response to this, they asked Michio Kaku to write something for them. They refer to him as a “cofounder of string theory”, which I suspect some people might object to. Presumably they meant to repeat what is in their profile of him, which calls him a “cofounder of string field theory.”

Kaku’s article is entitled Testing String Theory, and is a thoroughly intellectually dishonest piece of writing, designed to mislead anyone without expertise in what is at issue here. He succeeded in misleading whoever wrote the blurb for the article which goes: “No experiment has ever allowed us to test whether any of the assumptions of string theory are true. That is about to change.” No it’s not. None of the experiments Kaku mentions will “allow us to test whether any of the assumptions of string theory are true”.

As I’ve explained in detail on other occasions, the simple fact of the matter is that string theory does not make any predictions, unless one adopts a definition of the word “prediction” different than that conventional among scientists. A scientific prediction is one that tells you specifically what the results of a given experiment will be. If the results of the experiment come out differently, the theory is wrong. String theory can’t do this, since it is not a well-defined theory, but rather a research program that some people hope will one day lead to a well-defined theory capable of making predictions.

At places in the article Kaku qualifies his claims of “predictions”, for instance saying near the beginning of the article that certain experiments “could provide significant evidence that would support string theory” (note all the qualifiers in this phrase: “could”, “significant evidence”, “support”) but that “the rub is that all the new evidence, no matter how compelling, will still provide only indirect proof.” He soon abandons his qualified language and starts talking about the following topics:

1. Gravitational waves: He says of gravitational waves created in the Big Bang: “String theory predicts the frequencies of such waves”, and that this prediction will be tested by LISA. I don’t know specifically what he has in mind here, but I know of no way to use string theory to make a specific prediction of the spectrum of gravitational waves that LISA will see. The only things he mentions are inflation and epkyrotic scenarios, the first of which has nothing to do with string theory, the second very little.

2. The LHC: Kaku discusses the possibility that superpartners exist, but does note that you don’t need string theory to have these. He also discusses possible Tev-scale particle physics effects of extra dimensions, without mentioning that string theory makes no predictions at all about what these extra dimensions are like, or even what their size is. There is absolutely no reason other than wishful thinking to expect extra dimensions in string theory of a size invisible until now, but visible at LHC energies.

3. Laboratory tests of the inverse-square law: Kaku claims: “according to string theory, at small scales like a millimeter, gravity might hop across higher dimensions and perhaps into other, parallel universes”. This is a load of nonsense. String theory predicts no such thing. It may be consistent with this, purely because it is consistent with anything. He does go on to say “Perhaps the additional dimensions would show up only on smaller scales — string theory is still somewhat vague about this prediction.” “Somewhat vague”??? As far as I know string theory makes no prediction about this at all, except that most string theorists expect effects to show up below 10^-33cm, not 10^-1cm.

4. Dark matter searches: according to Kaku “Once particles of dark matter are identified in the laboratory, their properties can be analyzed and compared with the predictions of string theory.” Only problem is string theory makes no such predictions. He’s talking about neutralinos, but in string theory the neutralino mass could be absolutely anything. After discussing these string theory”predictions” about dark matter, he goes on to speculate that maybe there is no dark matter anyway, just “huge clumps of shadow matter in a parallel universe, causing our galaxies to form in mirror-image locations”, then admits that such an idea is incapable of ever being experimentally tested.

After going through all this, he saves the real kicker for the end: “Some theorists, myself among them, believe that the final verdict on string theory will not come from experiments at all”. So he doesn’t even believe in any of the nonsense he has been spouting. He admits that “The principal reason predictions of string theory are not well-defined is that the theory is not finished.” So the earlier talk of “predictions” is now no longer operative. He goes on to invoke the pipe dream that someday someone will come up with a finished version of string theory that will predict precisely the standard model, neglecting to mention that there’s not the slightest evidence that this is a realistic possibility. On the contrary, all the evidence now points to the conclusion that, if string theory makes sense at all, it has an infinity of different vacuum states, and is probably a radically non-predictive theory. Impressive that Kaku could write a whole article about the prospects of string theory, and somehow neglect to mention the huge and very relevant controversy surrounding the idea of the landscape. Do you think he hasn’t heard about it?

I’d been wondering why Lubos Motl seemed rather subdued in recent months, now one of his recent postings makes some reasons for this clear. Evidently since April he’s been the victim of someone who has been sending him grotesque anonymous death threats. Luckily the person responsible for this has now been identified by the police. In the comment section of the next entry in his blog, Eva Silverstein tells of also being the victim of similar threats, and again the police had to be called in.

Lubos’s participation in the controversy over the president of Harvard’s remarks about women in the sciences seems to have earned him both warnings from senior colleagues (I guess this is what his “leashing” was about), as well as harassment by some other anonymous figure. There’s no excuse for people trying to hide behind anonymity to engage in personal attacks. While Lubos is not known to completely refrain from personal attacks himself, at least he has always put his name to them.

In his latest posting he discusses in detail Silverstein and McGreevy’s claims that one can understand something about the initial singularity of the big bang in terms of tachyon condensation in string theory. Like Jacques Distler, he says that he doesn’t understand these claims, which to me seem to be a lot more coherent, but not of a significantly different nature than those of the Bogdanovs.

One of the big experimental HEP conferences, the Lepton-Photon Symposium, has just ended and many of the talks are on-line. This is the 22nd of these conferences which happen every two years. New data from the Tevatron about the top quark was discussed, and a paper with the new top quark mass results has been released.

There’s a new web-site with news about the LHC.

Last month there was an Einstein Symposium in Alexandria, and presentations are on-line. They’re for the general public so pretty content-free, but it is interesting to see what Witten’s latest view of string theory is: “I’d like to believe — but of course I don’t know — that string theory is on the right track…” Michio Kaku begins his presentation with advertisements for his books, then tells the audience that testing string theory would require creating a “baby universe”, that “Mind of God = music resonating through 11 dimensional hyperspace” and that the standard model is “supremely ugly” (which strikes me as something supremely stupid to say).

If you can’t wait for next week’s Strings 2005 in Toronto, there’s a summer school on strings going on at Perimeter, and a meeting in Crete that just ended, along with many more string conferences to come. The one series of talks I won’t be able to make it to, but would love to hear would be Graeme Segal’s talks in Oporto on 2d QFT.

The DOE has just announced the award of seven new Outstanding Junior Investigator grants in high-energy theory and experiment, one of which is going to Lubos Motl.

Via Steve Hsu, the news from the Wall Street Journal is that Renaissance Technologies is about to launch a new hedge fund that could end up managing $100 billion, 10% of the total managed by all hedge funds today.

Renaissance Technologies is run by mathematician Jim Simons, perhaps the most successful hedge fund manager ever. His current Medallion hedge fund manages $5 billion, and his personal net worth is estimated to be about $2.5 billion. Renaissance employs many Ph.D. mathematicians and other scientists, but is quite secretive about their investment strategies. If you ask people who are working there about what they are doing, you get answers like “I could tell you, but then I’d have to kill you.”

Simons was an undergraduate at MIT, got his Ph.D. from Berkeley in 1961, then was a junior faculty member at MIT and Harvard. He worked for a while at the Institute for Defense Analyses in Princeton, but was fired over criticism of the Vietnam War. He then went to SUNY Stony Brook, where as chair he built up a great math department, one especially strong in geometry. His work with Chern in the early seventies led to an extension of Chern-Weil theory involving “Chern-Simons forms”, which have been of great importance in physics.

During the seventies he started trading currencies and commodities with his own money, leaving Stony Brook in 1978 to form his own investment fund. Over the years he has been generous to the mathematics community, supporting MSRI, the IAS, the Stony Brook and MIT math departments, and many conferences and workshops. I have no idea what his long term plans are for his current billions or the additional ones his new hedge fund may generate, but if even a fraction of them end up financing pure math research, this could have a very dramatic effect.